Hollow CBT screw system reinforced by directional bone cement

Abstract

The invention relates to a directional bone cement reinforced hollow CBT screw system which comprises a screw head, a screw rod and a screw point, the near end of the screw head and the near end of the screw rod are connected with the bottom end of the screw head, the far end of the screw rod is provided with the screw point, the screw head is provided with a U-shaped groove, the near end of the screw rod is provided with a side hole positioning mark, the far end of the screw rod is provided with a side hole structure, and a hollow channel is formed in the screw rod. One end of the hollow channel is communicated with the bottom of the U-shaped groove, the other end of the hollow channel is communicated with the side hole structure, and a thread structure is arranged on the outer surface of the nail rod and comprises double threads and single threads. The anatomical targeting reinforcement of the screw is realized, and the risk of nerve and blood vessel injury is reduced; the direction of the screw is controllable in real time, and operation is convenient; the mechanical property of the screw is optimized, and the service life of an implant is prolonged; the cement distribution of the screw is plastic, the bone healing quality is improved, and the full-size adaptability of the screw meets the diversified clinical requirements from minimally invasive surgery to open surgery.

Description

Technical Field

[0001] The present invention relates to the technical field of orthopedic medical devices, and particularly to a hollow CBT screw system with directional bone cement reinforcement. Background Art

[0002] With the development of spinal surgery towards minimally invasive and precise directions, since the Cortical Bone Trajectory (CBT) screw technology was proposed, it has gradually become an important internal fixation solution for osteoporotic patients and revision surgeries. Compared with traditional pedicle screws, CBT screws achieve efficient utilization of cortical bone through a unique screw insertion path - starting from the lateral side of the articular process as the screw insertion point, tilting medially into the pedicle, and then turning laterally through the vertebral body. This design significantly reduces the intraoperative muscle dissection range, decreases the incidence of postoperative chronic low back pain, and at the same time, due to the screw being in close contact with high-density cortical bone throughout the process, it demonstrates better anti-pullout performance in osteoporotic patients. However, the contradiction between the clinical advantages of CBT screws and their biomechanical properties has gradually emerged: although the tight bite between the screw and cortical bone improves the initial stability, it also causes stress concentration at the screw-bone interface, which is prone to screw surrounding fractures or loosening under long-term loading. Especially for patients with severely insufficient bone density (such as postmenopausal osteoporosis or neoplastic bone destruction), the reliability solely relying on cortical bone anchoring is still insufficient.

[0003] To overcome this limitation, the orthopedic field has begun to explore the combination of bone cement strengthening technology and CBT screws. Hollow bone cement screws inject bone cement into the surrounding bone tissue through the channels in the screw body, and use the "anchoring effect" after cement curing to enhance the stability of the screw-bone interface. This concept has been successfully applied in traditional pedicle screws. However, when this technology is transferred to CBT screws, significant anatomical adaptability problems have emerged. The implantation trajectory of CBT screws is essentially different from that of traditional screws: its screw insertion point is more medial, and a large adduction angle (usually 15° - 25°) needs to be maintained during implantation, which makes the screw tail closer to the lateral region of the pedicle. The side holes of traditional hollow screws are mostly evenly distributed along the screw body or concentrated in the middle and posterior segments. After CBT screws are implanted, these side holes may be located in the cortical bone weak area at the junction of the pedicle and the vertebral body, or even completely exposed in dangerous areas such as the spinal canal and nerve root foramen. When bone cement overflows in such positions, it is extremely easy to leak along the loose cancellous bone spaces or anatomical fissures, resulting in serious complications such as nerve compression and vascular embolism. Clinical reports show that when using traditional hollow screws for CBT fixation, the bone cement leakage rate is significantly higher than that in the application scenario of traditional pedicle screws, and in some studies, the leakage rate even exceeds 30%, severely limiting the popularization of this technology.

[0004] In addition, the anatomical specificity of CBT screws poses unique requirements for the distribution pattern of bone cement. Since the distal end of CBT screws is usually located in the inner 1 / 3 region of the vertebral body, and important neurovascular structures are adjacent to the lateral side of the vertebral body, ideal cement diffusion should be concentrated in the central and inner cancellous bone regions of the vertebral body, forming an asymmetric "inner strengthening area". However, the side hole designs of existing hollow screws are mostly based on the concept of circumferential symmetric distribution (such as three holes evenly distributed at 120° or two holes distributed oppositely). After CBT screws are implanted, at least one side hole may face the dangerous area on the lateral side of the vertebral body. Even with a single-side hole design, there is a lack of a reliable means for positioning the direction of the side hole during the operation, and it is difficult for the operator to ensure that the side hole accurately faces the center of the vertebral body. This problem is particularly prominent in screws with a smaller diameter (such as 3.5 mm) - to maintain the strength of the screw, usually only a single side hole is provided for such screws, and once the direction deviates, the cement may be directly injected into non-target areas. Existing solutions mostly rely on repeated adjustment of the screw rotation angle under intraoperative fluoroscopy. However, the two-dimensional nature of fluoroscopic images cannot accurately reflect the orientation of the side hole in three-dimensional space, resulting in an extended operation time, increased radiation exposure, and still a relatively high operation error.

[0005] On the other hand, there is a contradiction between the structural characteristics of hollow screws and the biomechanical requirements of CBT screws. Due to the full-course engagement of cortical bone by CBT screws, they need to bear higher shear stress and torsional moment, which poses stringent requirements on the mechanical properties of the screws. Traditional hollow screws usually need to reduce the wall thickness of the screw body or increase the outer diameter to accommodate the bone cement channel, and the existence of side holes further weakens the structural integrity of the screw body. Research shows that after a single side hole is opened in a hollow screw with a diameter of 4.0 mm, its torsional strength can decrease by up to 40%, and it is prone to fatigue fracture under cyclic loading. In addition, the injection of bone cement may change the stress distribution pattern around the screw: if the cement is concentrated at the distal end of the screw body, it may form a "stress shield" with too high rigidity, which instead accelerates bone resorption around; if the distribution is uneven, the holding force cannot be effectively improved. The existing designs lack an active control mechanism for the cement diffusion path, resulting in the strengthening effect highly depending on the operator's experience and significant differences in clinical results.

[0006] Despite the above challenges, the potential value of bone cement-reinforced CBT screws cannot be ignored. For complex cases with severe osteoporosis, non-union of vertebral fractures, or the need for long-segment fixation, the anchoring effect of bone cement can significantly improve the immediate stability of the screws, providing a mechanical basis for bone healing. In addition, functional components such as radiopaque agents or antibiotics mixed in the bone cement can also achieve real-time imaging during the operation or local drug release, further expanding the clinical application scenarios. However, the existing technologies have not been systematically optimized for the anatomical and mechanical characteristics of CBT screws, resulting in the failure to fully convert their advantages into clinical benefits. How to design a side hole layout and direction control system to precisely strengthen the target area with bone cement while maintaining the structural strength and surgical operability of the screws has become a technical bottleneck that urgently needs to be broken through in this field.

[0007] In summary, the current technical defects of cement-reinforced CBT screws can be attributed to three major contradictions: First, the anatomical adaptability contradiction - the traditional side hole position does not match the CBT trajectory, resulting in an imbalance between the leakage risk and the reinforcement efficiency; Second, the mechanical property contradiction - the hollow structure and side holes weaken the screw strength and it is difficult to meet the high stress requirements of CBT; Third, the surgical controllability contradiction - the lack of precise direction control means makes the surgical outcome overly dependent on the surgeon's experience. The intertwined effects of these contradictions severely restrict the depth of application of the cement reinforcement technology in the CBT field.

[0008] Therefore, there is an urgent need for a hollow cement screw system optimized for CBT screws. Summary of the Invention

[0009] The present invention provides a hollow cement screw system optimized for CBT screws. Through innovative side hole layout design and visualization direction control technology, it realizes safe, efficient, and controllable cement reinforcement, and has clear clinical necessity and technological innovation value.

[0010] The present invention provides a hollow CBT screw system with directional cement reinforcement, including a screw head, a screw rod, and a screw tip. The proximal end of the screw rod is connected to the bottom end of the screw head, and the distal end of the screw rod is provided with the screw tip. Characterized in that, a U-shaped groove is provided on the screw head, a side hole positioning mark is provided at the proximal end of the screw rod, a side hole structure is provided at the distal end of the screw rod, a hollow channel is provided inside the screw rod, one end of the hollow channel communicates with the bottom of the U-shaped groove, the other end of the hollow channel communicates with the side hole structure, a thread structure is provided on the outer surface of the screw rod, the thread structure includes double threads and single threads, the double threads are provided on the outer surface of the side hole structure area of the screw rod, and the single threads are provided on the outer surface of the non-side hole area of the screw rod.

[0011] In the hollow CBT screw system with directional cement reinforcement, preferably, the side hole structure is located at the distal 1 / 3 of the screw rod.

[0012] In the hollow CBT screw system with directional cement reinforcement, preferably, the side hole structure includes a first side hole channel and a second side hole channel arranged longitudinally, and the angles between the axes of the first side hole channel and the second side hole channel and the axis of the screw rod are both 14-16°.

[0013] In the hollow CBT screw system with directional cement reinforcement, preferably, the calculation formula for the distance from the center of the hole of the first side hole channel or the second side hole channel to the screw head is:

[0014] Where, l is the distance from the center of the hole of the first side hole or the second side hole to the nail head; L is the total length of the screw.

[0015] For the hollow CBT screw system with directional bone cement reinforcement, preferably, the side hole positioning mark includes an annular scale and an arrow mark. The annular scale is arranged at the proximal end of the nail rod, and the arrow mark is provided on the annular scale.

[0016] For the hollow CBT screw system with directional bone cement reinforcement, preferably, when the diameter of the nail rod is greater than 3.5 mm, the diameters of the proximal entrances of the first side hole and the second side hole are 1.2 - 1.4 mm respectively, and the diameters of the distal entrances of the first side hole and the distal exits of the second side hole are 0.9 - 1.1 mm respectively.

[0017] For the hollow CBT screw system with directional bone cement reinforcement, preferably, when the diameter of the nail rod is not greater than 3.5 mm, the diameters of the proximal entrance and the distal exit of the first side hole are both 0.2 - 0.4 mm, the diameter of the proximal entrance of the second side hole is 0.9 - 1.1 mm, and the diameter of the distal exit of the second side hole is 0.7 - 0.9 mm.

[0018] The beneficial effects are as follows: 1. Precise anatomical adaptation and safety reinforcement.

[0019] The side hole is located at the 1 / 3 of the distal end of the nail rod and on the side away from the vertebral cortex after the vertebral screw is implanted. The diffusion range of the bone cement is strictly limited to the high - density cancellous bone area inside the vertebra, forming a "targeted anchorage area", significantly reducing the probability of cement leakage into dangerous areas such as the spinal canal and nerve root foramen. After the screw is implanted, the side hole always faces the central safety area of the vertebra, avoiding the risk of accidental leakage caused by anatomical misalignment in the traditional design, especially suitable for complex cases with a large adduction angle.

[0020] 2. The intraoperative operability is significantly improved.

[0021] The tail visual marking system provides real - time direction feedback for the operator. Through the coordinated action of the scale ring and the arrow mark, the operator can precisely control the orientation of the side hole without repeated fluoroscopy, significantly shortening the operation time and reducing radiation exposure. This design is especially beneficial for operations in a narrow surgical field during minimally invasive surgery, significantly reducing the manual adjustment error.

[0022] 3. The mechanical properties and structural reliability are improved.

[0023] The gradient anti-torsion strengthening strategy achieved through differential thread design effectively compensates for the weakening of the mechanical properties of the screw caused by the hollow structure and side holes, while maintaining the anti-fatigue characteristics of the screw under cyclic loading while ensuring the function of the bone cement flow channel. The pitch reduction and thread profile optimization in the side hole area further enhance the initial stability of the screw-bone interface, especially meeting the load-bearing requirements of CBT screws for high shear stress.

[0024] 4. Enhanced full-size screw adaptability.

[0025] The graded hole number strategy based on the screw diameter balances the mechanical properties of screws of different specifications and the requirements for cement perfusion. The small-diameter screw ensures the minimum required cement flow through the micro-hole auxiliary design, while the multi-hole layout of the large-diameter screw achieves efficient strengthening without significantly weakening the structural strength, providing a universal solution for diverse clinical cases.

[0026] 5. Extended clinical indications and long-term stability.

[0027] The present invention enables the safe application of the bone cement strengthening technology to high-risk patients such as severe osteoporosis and vertebral tumor defects. It improves the immediate stability through precise anchoring, and at the same time, the optimized cement distribution pattern reduces the "stress shielding effect" and promotes the long-term biological integration of the bone-screw interface.

[0028] The present invention realizes the anatomical targeted strengthening of the screw, reduces the risk of neurovascular injury, and expands the surgical safety margin; the direction of the screw is controllable in real time, shortens the operation time, and reduces the radiation exposure of doctors and patients; it optimizes the mechanical properties of the screw to extend the service life of the implant and reduce the probability of revision surgery; the cement distribution of the screw is plastic, improves the quality of bone healing, reduces the risk of secondary fractures after surgery, and the full-size adaptability of the screw meets the diverse clinical needs from minimally invasive to open surgery. Brief Description of the Drawings

[0029] Figure 1 is a schematic structural diagram of the present invention; Figure 2 is a schematic structural diagram of the hollow channel and the side hole; Figure 3 is a schematic structural diagram of the hollow channel and the side hole; Figure 4 is a schematic structural diagram of the positioning mark.

[0030] In the figure: 1, screw head; 2, screw rod; 3, screw tip; 4, U-shaped groove; 5, hollow channel; 6, double thread; 7, single thread; 8, first side hole channel; 8-1, proximal entrance of the first side hole channel; 8-2, distal exit of the first side hole channel; 9. Second side channel; 9-1. Proximal inlet of the second side channel; 9-2. Distal outlet of the second side channel 10. Ring scale; 11. Arrow mark. Detailed implementation mode

[0031] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] In the description of the present invention, it should be noted that the orientation or positional relationships indicated by the terms "distal", "proximal", "one end", "the other end" and "bottom", etc. are based on the orientation or positional relationships shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the system or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation to the present invention. In addition, the use of terms such as "first" and "second" to define components is only for the convenience of distinguishing the above components. Without further statement, the above terms have no special meanings and cannot be construed as indicating or implying relative importance.

[0033] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "set" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0034] A hollow CBT screw system with directional bone cement reinforcement provided by the present invention includes a screw head, a screw rod, and a screw tip. The proximal end of the screw rod is connected to the bottom end of the screw head, and the distal end of the screw rod is provided with the screw tip. It is characterized in that the screw head is provided with a U-shaped groove, the proximal end of the screw rod is provided with a side hole positioning mark, the distal end of the screw rod is provided with a side hole structure, a hollow channel is arranged inside the screw rod, one end of the hollow channel is communicated with the bottom of the U-shaped groove, the other end of the hollow channel is communicated with the side hole structure, the outer surface of the screw rod is provided with a thread structure, the thread structure includes a double thread and a single thread, the double thread is arranged on the outer surface of the side hole structure area of the screw rod, and the single thread is arranged on the outer surface of the non-side hole area of the screw rod. The present invention realizes the anatomical targeting reinforcement of the screw, reduces the risk of neurovascular injury, expands the surgical safety margin, the direction of the screw is controllable in real time, shortens the operation time, reduces the radiation exposure of doctors and patients, optimizes the mechanical properties of the screw to extend the service life of the implant and reduce the probability of revision surgery, the cement distribution of the screw is plastic, improves the bone healing quality, reduces the risk of secondary fracture after surgery, and the full-size adaptability of the screw meets the diverse clinical needs from minimally invasive to open surgery.

[0035] The following takes a hollow CBT screw system with directional bone cement reinforcement as an example to elaborate the entire technical process in detail.

[0036] As Figures 1 to 4 shown, a hollow CBT screw system with directional bone cement reinforcement includes a screw head 1, a screw rod 2, and a screw tip 3. The proximal end of the screw rod 2 is connected to the bottom end of the screw head 1, the distal end of the screw rod 2 is provided with the screw tip 3, the screw head 1 is provided with a U-shaped groove 4, the proximal end of the screw rod 2 is provided with a side hole positioning mark, the distal end of the screw rod 2 is provided with a side hole structure, a hollow channel 5 is arranged inside the screw rod 2, one end of the hollow channel 5 is communicated with the bottom of the U-shaped groove 4, the other end of the hollow channel 5 is communicated with the side hole structure, the outer surface of the screw rod 2 is provided with a thread structure, the thread structure includes a double thread 6 and a single thread 7, the double thread 6 is arranged on the outer surface of the side hole structure area of the screw rod 2, and the single thread 7 is arranged on the outer surface of the non-side hole area of the screw rod 2.

[0037] Among them, the side hole structure is located at the 1 / 3 position of the distal end of the screw rod 2.

[0038] The side hole structure includes a first side hole channel 8 and a second side hole channel 9 arranged longitudinally. The included angles between the axes of the first side hole channel 8 and the second side hole channel 9 and the axis of the screw rod 2 are both 14-16°, preferably, the included angles between the axes of the first side hole channel 8 and the second side hole channel 9 and the axis of the screw rod 2 are both 15°.

[0039] The calculation formula for the distance from the hole center of the first side hole channel 8 or the second side hole channel 9 to the screw head is:

[0040] Among them, l is the distance from the center of the hole of the first side channel or the second side channel to the nail head; L is the total length of the screw.

[0041] The positioning mark includes an annular scale 10 and an arrow mark 11. The annular scale 10 is arranged at the proximal end of the nail rod 2, and the arrow mark 11 is provided on the annular scale 10.

[0042] As Figure 2 shown, when the diameter of the nail rod 2 is greater than 3.5 mm, the diameters of the proximal entrances 8-1 of the first side channel and 9-1 of the second side channel are 1.2 - 1.4 mm respectively, and the diameters of the distal entrances 8-2 of the first side channel and the distal exits 9-2 of the second side channel are 0.9 - 1.1 mm respectively. Preferably, the diameters of the proximal entrances 8-1 of the first side channel and 9-1 of the second side channel are 1.3 mm respectively, and the diameters of the distal entrances 8-2 of the first side channel and the distal exits 9-2 of the second side channel are 1.0 mm respectively.

[0043] As Figure 3 shown, when the diameter of the nail rod 2 is not greater than 3.5 mm, the diameters of the proximal entrance 8-1 of the first side channel and the distal exit 8-2 of the first side channel are both 0.2 - 0.4 mm, the diameter of the proximal entrance 9-1 of the second side channel is 0.9 - 1.1 mm, and the diameter of the distal exit 9-2 of the second side channel is 0.7 - 0.9 mm. Preferably, the diameters of the proximal entrance 8-1 of the first side channel and the distal exit 8-2 of the first side channel are both 0.3 mm, the diameter of the proximal entrance 9-1 of the second side channel is 1.0 mm, and the diameter of the distal exit 9-2 of the second side channel is 0.8 mm. At this time, the first side channel 8 is equivalent to a microchannel, and the second side channel 9 is equivalent to a main side channel.

[0044] Example 1 1. Structural parameters The diameter of the nail rod 2 is 4.5 mm, the total length of the nail head 1, the nail rod 2 and the nail tip 3 is 40 mm, the inner diameter of the hollow channel 5 is 1.5 mm, the wall thickness of the nail rod 2 is 0.7 mm, the pitch of the double thread 6 at the distal end of the nail rod 2 is 2.5 mm, the depth is 1.2 mm, the pitch of the single thread 7 at the proximal end of the nail rod 2 is 2.0 mm, and the depth is 0.8 mm.

[0045] The nail rod 2 is provided with a first side channel 8 and a second side channel 9. The proximal entrances 8-1 of the first side channel, the proximal entrances 9-2 of the second side channel, the distal exits 8-2 of the first side channel, and the distal exits 9-2 of the second side channel are elliptical in shape. The distances between the first side channel 8 and the second side channel 9 and the nail tip 3 are 12 mm and 8 mm respectively, and the longitudinal spacing between the first side channel 8 and the second side channel 9 is 4 mm.

[0046] Aperture design: The diameters of the proximal entrances 8-1 of the first side channel and the proximal entrances 9-2 of the second side channel are 1.3 mm respectively, the diameters of the distal exits 8-2 of the first side channel and the distal exits 9-2 of the second side channel are 1.0 mm respectively, and the angles between the axes of the first side channel 8 and the second side channel 9 and the axis of the nail rod 2 are 15°; The length of the arrow mark 11 is 4 mm and the width is 0.8 mm. The arrow tip of the arrow mark 11 points to the directions of the distal exits 8-2 of the first side hole and the distal exits 9-2 of the second side hole.

[0047] The circumference of the annular dial 10 is 5 mm, with 36 equally divided scale lines (at 10° intervals), and the scale depth is 0.1 mm.

[0048] 2. Manufacturing process The material is medical titanium alloy (Ti-6Al-4V ELI, meeting ASTM F136 standard).

[0049] The processing flow of the screw of a hollow CBT screw system with directional bone cement reinforcement: Step 1: The nail head 1, the nail rod 2, the nail tip 3 and the hollow channel are machined by a numerical control machine tool.

[0050] Step 2: A five-axis laser drilling machine is used to open the first side channel 8 and the second side channel 9 to ensure the taper and angular accuracy of the channels of the first side channel 8 and the second side channel 9.

[0051] Step 3: The annular dial 10 and the arrow mark 11 are laser-etched. The coaxiality between the arrow of the arrow mark 11 and the first side channel 8 and the second side channel 9 is calibrated through an optical alignment system, and the error is <2°.

[0052] Step 4: The surfaces of the nail head 1, the nail rod 2 and the nail tip 3 are sandblasted (Ra = 3.2 μm) to enhance the bone integration performance.

[0053] 3. Operating steps Using the implantation method of a hollow CBT screw system with directional bone cement reinforcement in Example 1, it specifically includes the following steps: In the first step, implant a guide pin at the CBT standard entry point, and confirm the entry angle with a C-arm. Among them, the adduction angle is 20°.

[0054] In the second step, insert a hollow CBT screw system with directional bone cement reinforcement along the guide pin. Adjust the rotation angle through the arrow mark 11, and confirm through lateral fluoroscopy so that the arrow of the arrow mark 11 points to the center of the vertebral body.

[0055] In the third step, connect the bone cement injection system and inject high-viscosity bone cement at a pressure of 1.8 - 2.2 MPa.

[0056] In the fourth step, monitor the diffusion range of the high-viscosity bone cement through fluoroscopy, and stop injection when the high-viscosity bone cement reaches 8 mm distal to the distal end of the distal outlet 9 - 2 of the second side hole.

[0057] Among them, the key points for implementing the technical solution are as follows: (1) Side hole positioning rule:

[0058] Among them, l is the distance from the hole center of the first side hole or the second side hole to the nail head; L is the total length of the screw.

[0059] Open hole angle calibration method: Fix the screw on a V-shaped fixture, and verify the deflection angle with a laser projector.

[0060] (2) Marking system calibration: Use a coordinate measuring machine to detect the coaxiality between the tail arrow and the axis of the side hole. When the deviation > 2°, repair it.

[0061] (3) Bone cement injection control: Recommended cement viscosity: 25,000 - 30,000 cps (25 °C).

[0062] Injection termination condition: In lateral fluoroscopy, see that the front end of the cement is ≥ 5 mm from the anterior edge of the vertebral body.

[0063] Finally, it should be noted that: The above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: They can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A hollow CBT screw system with directional bone cement reinforcement, comprising a screw head, a screw shaft and a screw tip, wherein the screw head, the proximal end of the screw shaft is connected to the bottom end of the screw head, and the distal end of the screw shaft is provided with the screw tip, characterized in that, The nail head is provided with a U-shaped groove, the proximal end of the nail rod is provided with a side hole positioning mark, the distal end of the nail rod is provided with a side hole structure, the nail rod is provided with a hollow channel, one end of the hollow channel communicates with the bottom of the U-shaped groove, the other end of the hollow channel communicates with the side hole structure, the outer surface of the nail rod is provided with a thread structure, the thread structure includes double threads and single threads, the double threads are provided on the outer surface of the side hole structure area of the nail rod, and the single threads are provided on the outer surface of the non-side hole area of the nail rod.

2. The hollow CBT screw system with directional bone cement reinforcement according to claim 1, wherein The side hole structure is located at the 1 / 3 position of the distal end of the nail rod.

3. The hollow CBT screw system with directional bone cement reinforcement according to claim 2, wherein, The side hole structure includes a first side hole channel and a second side hole channel arranged longitudinally, and the angles between the axes of the first side hole channel and the second side hole channel and the axis of the nail rod are both 14-16°.

4. The hollow CBT screw system with directional bone cement reinforcement according to claim 3, characterized in that, The calculation formula for the distance between the hole center of the first side hole channel or the second side hole channel and the nail head is: Where, l is the distance between the hole center of the first side hole channel or the second side hole channel and the nail head; L is the total length of the screw.

5. The hollow CBT screw system with directional bone cement reinforcement according to claim 4, characterized in that, The side hole positioning mark includes an annular scale disk and an arrow mark, the annular scale disk is arranged at the proximal end of the nail rod, and the arrow mark is provided on the annular scale disk.

6. The hollow CBT screw system with directional bone cement reinforcement according to claim 5, characterized in that When the diameter of the nail rod is greater than 3.5 mm, the diameters of the proximal entrances of the first side hole channel and the second side hole channel are 1.2-1.4 mm respectively, and the diameters of the distal entrances of the first side hole channel and the distal exits of the second side hole channel are 0.9-1.1 mm respectively.

7. The hollow CBT screw system with directional bone cement reinforcement according to claim 6, characterized in that, When the diameter of the nail rod is not greater than 3.5 mm, the diameters of the proximal entrance and the distal exit of the first side hole channel are both 0.2-0.4 mm, the diameter of the proximal entrance of the second side hole channel is 0.9-1.1 mm, and the diameter of the distal exit of the second side hole channel is 0.7-0.9 mm.

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